1. Field of the Invention
The present invention relates to a reading apparatus for reading a target object having a fine recessed or projecting pattern such as a fingerprint.
2. Description of the Related Art
A conventional reading apparatus for reading a target object having a fine recessed or projecting pattern such as a fingertip has a structure like the one disclosed in U.S. Pat. No. 5,635,723 in which a two-dimensional photosensor is formed on a surface light source, and an optical component is formed on the two-dimensional photosensor. The invention of this reference detects changes in capacitance when a finger touches the optical component, and sequentially detects the detection results as electric charges, which are generated by photosensors arranged two-dimensionally and correspond to an incident light quantity from the optical component. In this structure, many light guide fibers are mounted on the two-dimensional photosensor without any optical lens, so that the whole apparatus can be downsized. Recently, another type of structure is examined in which an optical component formed from many light guide fibers is made thinner into a light scattering film or in which the upper surface of a photosensor is covered with a transparent resin layer having an uneven surface without any optical component. For example, this type of structure is disclosed in U.S. patent application Ser. No. 09/128,237 (Aug. 3, 1998) filed by the present applicant.
In this reading apparatus, a finger directly touches the upper surface of the two-dimensional photosensor. If the finger is charged with static electricity, this static electricity may cause a malfunction of the two-dimensional photosensor or may damage it in the worst case. If the pattern of a fingerprint is copied onto a sheet by any means, since the reading apparatus is not equipped with any means for discriminating a sheet from a human finger, the apparatus determines matching so long as the pattern is the same. When this fingerprint matching is set as a log-in condition for a personal computer or a host computer of a network, the computer cannot be reliably protected from a third person""s access.
It is the first object of the present invention to provide a reading apparatus which prevents a photosensor from malfunction or damage by static electricity. It is the second object of the present invention to provide a reading apparatus capable of ensuring the reliability by reading a pattern after, e.g., detecting whether the object is man.
According to the present invention, there is provided a reading apparatus for reading a target object comprising: a photosensor module having a plurality of photosensors arranged at least one plane; and a transparent conductive layer provided between the target object and the photosensor module.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.